A Better Mosquito Net

A Better Mosquito Net

Fighting malaria will require more innovative defenses

Malaria remains one of the world’s great scourges, striking more than 500 million people every year. The groups most at risk are pregnant women and children younger than five years old. In sub-Saharan Africa, 20 percent of all childhood deaths are from malaria. Pregnant women who contract the mosquito-borne disease can develop severe anemia and give birth to underweight babies. The World Health Organization estimates that 10,000 pregnant woman and 200,000 infants in Africa die from malarial infections every year.

To combat the disease, many development agencies have focused on distributing mosquito nets that would protect Africans from being bitten while they sleep. This strategy has resulted in a huge upsurge in the number of bed nets supplied to the population as a whole and particularly to pregnant women and young children. The widespread distribution, however, has not resulted in a significant decrease in malaria. Many doctors in sub-Saharan Africa attribute the failure to an overreliance on nets in lieu of other interventions, such as the indoor spraying of dwellings with insecticide. Other experts say the problem is the misuse of mosquito nets; there is anecdotal evidence that some people have employed the nets as wedding veils or fishing aids. Some economists argue that charging a small fee for the nets would increase the likelihood that they would be used appropriately. Others claim such a fee would prevent a large part of the population from receiving nets. These are valuable debates. Before delving into behavioral economics, though, it might be useful to consider a more basic problem: the mosquito nets are poorly designed.

The bed nets distributed by governments and international organizations have one of two basic designs: circular or rectangular. The circular design hangs from the ceiling by one string, with the net fanning out from a ring at the top and tucked tightly under the mattress on all sides. The rectangular design ties to the ceiling with four strings and hangs straight down on all sides of the bed, with the fringes again tucked under the mattress. Both designs work well for middle-class homes with flat ceilings and a bed for every member of the family. But most of the poor in sub-Saharan Africa, especially in rural areas, live in mud huts, often with thatched roofs.

Hanging mosquito nets is very difficult in these homes, and most people prefer the circular nets because they are easier to hang. Although the rectangular nets can be used without a bed, the circular nets cannot, because they have to be tucked under the mattress to fan out. In many African communities, most children younger than five sleep on the floor, so only the rectangular nets would be effective. But the rectangular nets take up quite a bit of room in a mud hut and have to be taken down and rehung every night for the hut to be of use during the day. Given the difficulty of hanging the nets, it is unreasonable to expect people to follow this routine.

A design more suited to the needs of young children would be a net that does not hang at all. One possibility would be a collapsible, tentlike structure, very similar to the crawl-through children’s toys that clutter so many playrooms in the U.S. The challenge would be to make the structure both affordable to produce and durable enough to be used daily for years. In addition to being user-friendly, this free-standing mosquito net would have to be sized for children to ensure that it is used by the intended recipients rather than older, hardier members of the family.

Mosquito nets have been changed before to meet user needs. Several companies have recently introduced nets that are impregnated with long-lasting insecticide, eliminating the need for people to continually apply fresh coatings of chemicals to the nets. Companies must continue to improve mosquito nets if progress is to be made in combating malaria. And once better nets are available, researchers will be able to objectively judge the effectiveness of the distribution programs.

Self-Powered Nanotech

Self-Powered Nanotech

Nanosize machines need still tinier power plants 

 
Powered by a nano?generator (foreground) that draws energy from the ambient environment, a sensor measures blood glucose or pressure in this conceptual image.

• Nano­technology has huge potential—but those minuscule devices will need a power source that is better than a battery.
• Waste energy, in the form of vibrations or even the human pulse, could provide sufficient power to run such tiny gadgets.
• Arrays of piezoelectric nano­wires could capture and transmit that waste energy to nano­devices.
• Medical devices will likely be a major application. A pacemaker’s battery could be charged so it would not need replacing, or implanted wireless nano­sensors could monitor blood glucose for diabetics.

The watchmaker in the 1920s who de­vised the self-winding wristwatch was on to a great idea: mechanically harvesting energy from the wearer’s moving arm and putting it to work rewinding the watch spring.

Today we are beginning to create extremely small energy harvesters that can supply electrical power to the tiny world of nano­scale devices, where things are measured in billionths of a meter. We call these power plants nano­generators. The ability to make power on a minuscule scale allows us to think of implantable biosensors that can continuously monitor a patient’s blood glucose level, or autonomous strain sensors for structures such as bridges, or environmental sensors for detecting toxins—all running without the need for replacement batteries. Energy sources are desperately needed for nano­robotics, microelectromechanical systems (MEMS), homeland security and even portable personal electronics. It is hard to imagine all the uses such infinitesimal generators may eventually find.

Signaling Neurons Make Neighbor Cells "Want In"

Signaling Neurons Make Neighbor Cells "Want In"

Synapses are primed to strengthen (and thus enable learning) if a neighbor has just been stimulated 

 
HELP THY NEIGHBOR: When an electrical signal crosses a synapse, the spines strengthen, enabling better communication. A residual effect, however, has now been found to aid in strengthening neighboring synapses, as well.

A new discovery about the function of neurons could help scientists understand how the brain assembles information during learning and memory formation.

Scientists have found that when electrical impulses are passed from one neuron to another, they not only strengthen the synapse (connection) between them, but they also give a boost to neighboring synapses, priming them to learn more quickly and easily. Researchers report in Nature that the extra kick, which lasts from five to 10 minutes, may be key to memory formation.

The residual effect "had been predicted based on so-called classic models of plasticity"—the ability of the brain to adapt by strengthening or weakening connections between neurons—but had not previously been proved, says study co-author Karel Svoboda, a biophysics group leader at the Howard Hughes Medical Institute's Janelia Farm Research Campus in Ashburn, Va. "You'd like to have clustered plasticity of this sort" to keep memories grouped together.

Neurons, or nerve cells, each have a pair of projections—the axon and the dendrite, which transmit and receive impulses, respectively. The dendrite, a treelike structure, has several branches dotted with hundreds synaptic receiving terminals called "spines," each connected to the axons of scores of other neurons. When one of these spines receives stimulation (through the synapse it creates with another cell's axonal projection), the spine expands into the synapse, strengthening the link between its neuron and the other cell. This process of enhanced communication through a synapse is called long-term potentiation (LTP) and is thought to be the basis of learning.

Previous attempts to identify this process were stymied by inexact methods. Researchers primarily used electrical impulses, which do not allow for good spatial observation. Svoboda and study co-author Christopher Harvey, a graduate student in Svoboda's lab, used a more precise technique. They attached a light-absorbing chemical group to the neurotransmitter glutamate (an excitatory chemical messenger in the brain) at a particular synapse in a slice of a rat's hippocampus, the brain region responsible for short-term memory. When they trained a laser on the glutamate, it was freed from its light-absorbing molecular captor and thereby able to resume its function; it went to the dendritic spine in the synapse, allowing ions to enter the cell and an electrical signal to be generated.

As a result of this stimulation, the spine stretched farther into the synapse. Researchers did not find any evidence that neighboring spines had also expanded, but they did find that it took less stimulation—only 20 percent of the original prodding—to prompt any of the 20 spines within 10 microns (around four ten-thousandths of an inch) to undergo LTP. This effect appeared to last for five to 10 minutes, the scientists report.

Svoboda says that this cooperative activity may underlie how information is integrated when, for instance, an individual enters a new environment and looks around making associations of different cues within that space. "People didn't know how these associations over the course of 10 minutes or so could be coded in neurons," he says. "It provides a possible mechanism for associations over minutes."

In an editorial accompanying the article, Bernardo Sabatini, an assistant professor of neurobiology at Harvard Medical School, says that Harvey and Svoboda's work introduces new complexity into the brain's neuronal wiring.

"[For] some forms of activity-dependent plasticity in the hippocampus, the fundamental unit of regulation might be larger than an individual synapse," he wrote, "and, rather, a physically clustered cohort of synapses with similar firing patterns, whose spatial arrangement on dendrites arises naturally follow mutually reinforcing interactions between synapses."

Evonomics

Evonomics

Evolution and economics are both examples of a larger mysterious phenomenon

Living along the Orinoco River that borders Brazil and Venezuela are the Yanomamö people, hunter-gatherers whose average annual income has been estimated at the equivalent of $90 per person per year. Living along the Hudson River that borders New York State and New Jersey are the Manhattan people, consumer-traders whose average annual income has been estimated at $36,000 per person per year. That dramatic difference of 400 times, however, pales in comparison to the differences in Stock Keeping Units (SKUs, a measure of the number of types of retail products available), which has been estimated at 300 for the Yanomamö and 10 billion for the Manhattans, a difference of 33 million times! How did this happen? According to economist Eric D. Beinhocker, who published these calculations in his revelatory work The Origin of Wealth (Harvard Business School Press, 2006), the explanation is to be found in complexity theory. Evolution and economics are not just analogous to each other, but they are actually two forms of a larger phenomenon called complex adaptive systems, in which individual elements, parts or agents interact, then process information and adapt their behavior to changing conditions. Immune systems, ecosystems, language, the law and the Internet are all examples of complex adaptive systems.

In biological evolution, nature selects from the variation produced by random genetic mutations and the mixing of parental genes. Out of that process of cumulative selection emerges complexity and diversity. In economic evolution, our material economy proceeds through the production and selection of numerous permutations of countless products. Those 10 billion products in the Manhattan village represent only those variations that made it to market, after which there is a cumulative selection by consumers in the marketplace for those deemed most useful: VHS over Betamax, DVDs over VHS, CDs over vinyl records, flip phones over brick phones, computers over typewriters, Google over Altavista, SUVs over station wagons, paper books over e-books (still), and Internet news over network news (soon). Those that are purchased “survive” and “reproduce” into the future through repetitive use and remanufacturing.

As with living organisms and ecosystems, the economy looks designed—so just as humans naturally deduce the existence of a top-down intelligent designer, humans also (understandably) infer that a top-down government designer is needed in nearly every aspect of the economy. But just as living organisms are shaped from the bottom up by natural selection, the economy is molded from the bottom up by the invisible hand.

The correspondence between evolution and economics is not perfect, because some top-down institutional rules and laws are needed to provide a structure within which free and fair trade can occur. But too much top-down interference into the marketplace makes trade neither free nor fair. When such attempts have been made in the past, they have failed—because markets are far too complex, interactive and autocatalytic to be designed from the top down. In his 1922 book, Socialism, Ludwig von Mises spelled out the reasons why, most notably the problem of “economic calculation” in a planned socialist economy. In capitalism, prices are in constant and rapid flux and are determined from below by individuals freely exchanging in the marketplace. Money is a means of exchange, and prices are the information people use to guide their choices. Von Mises demonstrated that socialist economies depend on capitalist economies to determine what prices should be assigned to goods and services. And they do so cumbersomely and inefficiently. Relatively free markets are, ultimately, the only way to find out what buyers are willing to pay and what sellers are willing to accept.

Evonomics helps to explain how Yanomamö-like hunter-gatherers evolved into Manhattan-like consumer-traders. Nineteenth-century French economist Frédéric Bastiat well captured the principle: “Where goods do not cross frontiers, armies will.” In addition to being fierce warriors, the Yanomamö are also sophisticated traders, and the more they trade the less they fight. The reason is that trade is a powerful social adhesive that creates political alliances. One village cannot go to another village and announce that they are worried about being conquered by a third, more powerful village—that would reveal weakness. Instead they mask the real motives for alliance through trade and reciprocal feasting. And, as a result, not only gain military protection but also initiate a system of trade that—in the long run—leads to an increase in both wealth and SKUs.

Global food supply is dwindling rapidly, UN agency warns

Global food supply is dwindling rapidly, UN agency warns

The world food supply is dwindling rapidly and food prices are soaring to historic levels, the top food and agriculture official of the United Nations warned Monday.

In an "unforeseen and unprecedented" shift, the world food supply is dwindling rapidly and food prices are soaring to historic levels, the top food and agriculture official of the United Nations warned Monday.

The changes created "a very serious risk that fewer people will be able to get food," particularly in the developing world, said Jacques Diouf, head of the UN Food and Agriculture Organization.

The agency's food price index rose by more than 40 percent this year, compared with 9 percent the year before - a rate that was already unacceptable, he said. New figures show that the total cost of foodstuffs imported by the neediest countries rose 25 percent, to $107 million, in the last year.

At the same time, reserves of cereals are severely depleted, FAO records show. World wheat stores declined 11 percent this year, to the lowest level since 1980. That corresponds to 12 weeks of the world's total consumption - much less than the average of 18 weeks consumption in storage during the period 2000-2005. There are only 8 weeks of corn left, down from 11 weeks in the earlier period.

Prices of wheat and oilseeds are at record highs, Diouf said Monday. Wheat prices have risen by $130 per ton, or 52 percent, since a year ago. U.S. wheat futures broke $10 a bushel for the first time Monday, the agricultural equivalent of $100 a barrel oil. (Page 16)

Diouf blamed a confluence of recent supply and demand factors for the crisis, and he predicted that those factors were here to stay. On the supply side, these include the early effects of global warming, which has decreased crop yields in some crucial places, and a shift away from farming for human consumption toward crops for biofuels and cattle feed. Demand for grain is increasing with the world population, and more is diverted to feed cattle as the population of upwardly mobile meat-eaters grows.

"We're concerned that we are facing the perfect storm for the world's hungry," said Josette Sheeran, executive director of the World Food Program, in a telephone interview. She said that her agency's food procurement costs had gone up 50 percent in the past 5 years and that some poor people are being "priced out of the food market."

To make matters worse, high oil prices have doubled shipping costs in the past year, putting enormous stress on poor nations that need to import food as well as the humanitarian agencies that provide it.

"You can debate why this is all happening, but what's most important to us is that it's a long-term trend, reversing decades of decreasing food prices," Sheeran said.

Climate specialists say that the vulnerability will only increase as further effects of climate change are felt. "If there's a significant change in climate in one of our high production areas, if there is a disease that effects a major crop, we are in a very risky situation," said Mark Howden of the Commonwealth Scientific and Industrial Research Organization in Canberra.

Already "unusual weather events," linked to climate change - such as droughts, floods and storms - have decreased production in important exporting countries like Australia and Ukraine, Diouf said.

In Southern Australia, a significant reduction in rainfall in the past few years led some farmers to sell their land and move to Tasmania, where water is more reliable, said Howden, one of the authors of a recent series of papers in the Procedings of the National Academy of Sciences on climate change and the world food supply.

"In the U.S., Australia, and Europe, there's a very substantial capacity to adapt to the effects on food - with money, technology, research and development," Howden said. "In the developing world, there isn't."

Sheeran said, that on a recent trip to Mali, she was told that food stocks were at an all time low. The World Food Program feeds millions of children in schools and people with HIV/AIDS. Poor nutrition in these groups increased the risk serious disease and death.

Diouf suggested that all countries and international agencies would have to "revisit" agricultural and aid policies they had adopted "in a different economic environment." For example, with food and oil prices approaching record, it may not make sense to send food aid to poorer countries, but instead to focus on helping farmers grow food locally.

FAO plans to start a new initiative that will offer farmers in poor countries vouchers that can be redeemed for seeds and fertilizer, and will try to help them adapt to climate change.

The recent scientific papers concluded that farmers could adjust to 1 degree Celsius (1.8 degrees Fahrenheit) to 3 degrees Celsius (5.4 degrees) of warming by switching to more resilient species, changing planting times, or storing water for irrigation, for example.

But that after that, "all bets are off," said Francesco Tubiello, of Columbia University Earth Institute. "Many people assume that we will never have a problem with food production on a global scale, but there is a strong potential for negative surprises."

In Europe, officials said they were already adjusting policies to the reality of higher prices. The European Union recently suspended a "set-aside" of land for next year - a longstanding program that essentially paid farmers to leave 10 percent of their land untilled as a way to increase farm prices and reduce surpluses. Also, starting in January, import tariffs on all cereal will be eliminated for six months, to make it easier for European countries to buy grain from elsewhere. But that may make it even harder for poor countries to obtain the grain they need.

In an effort to promote free markets, the European Union has been in the process of reducing farm subsidies and this has accelerated the process.

"It's much easier to do with the new economics," said Michael Mann a spokesman for the EU agriculture commission. "We saw this coming to a certain extent, but we are surprised at how quickly it is happening."

But he noted that farm prices the last few decades have been lower than at any time in history, so the change seems extremely dramatic.

Diouf noted that there had been "tension and political unrest related to food markets" in a number of poor countries this year, including Morocco, Senegal and Mauritania. "We need to play a catalytic role to quickly boost crop production in the most affected countries," he said.

Part of the current problem is an outgrowth of prosperity. More people in the world now eat meat, diverting grain from humans to livestock. A more complicated issue is the use of crops to make biofuels, which are often heavily subsidized. A major factor in rising corn prices globally is that many farmers in the United States are now selling their corn to make subsidized ethanol.

Mann said the European Union had intentionally set low targets for biofuel use - 10 per cent by 2020 - to limit food price rises and that it plans to import some biofuel. "We don't want all our farmers switching from food to biofuel," he said.